To recite "In the name of Allah," during every action and on having sexual relations with one's wife
حَدَّثَنَا عَلِيُّ بْنُ عَبْدِ اللَّهِ، قَالَ حَدَّثَنَا جَرِيرٌ، عَنْ مَنْصُورٍ، عَنْ سَالِمِ بْنِ أَبِي الْجَعْدِ، عَنْ كُرَيْبٍ، عَنِ ابْنِ عَبَّاسٍ، يَبْلُغُ بِهِ النَّبِيَّ صلى الله عليه وسلم قَالَ " لَوْ أَنَّ أَحَدَكُمْ إِذَا أَتَى أَهْلَهُ قَالَ بِسْمِ اللَّهِ اللَّهُمَّ جَنِّبْنَا الشَّيْطَانَ وَجَنِّبِ الشَّيْطَانَ مَا رَزَقْتَنَا. فَقُضِيَ بَيْنَهُمَا وَلَدٌ، لَمْ يَضُرَّهُ ".
Narrated Ibn `Abbas: The Prophet (ﷺ) said, "If anyone of you on having sexual relations with his wife said (and he must say it before starting) 'In the name of Allah. O Allah! Protect us from Satan and also protect what you bestow upon us (i.e. the coming offspring) from Satan, and if it is destined that they should have a child then, Satan will never be able to harm that offspring."